Moon spotted orbiting distant dwarf planet

Kuiper Belt objects have spiked the curiosity of astronomers for years now and as a result of this we continue to make new discoveries with each passing day.

One such discovery is that of a moon orbiting the third largest dwarf planet we know. The dwarf planet resides in the frigid outskirts of our solar system – the Kuiper Belt. The moon orbits the dwarf planet 2007 OR10 in the Kuiper Belt, a realm of icy debris left over from our solar system’s formation 4.6 billion years ago.

Astronomers say that this particular discovery means that most of the known dwarf planets in the Kuiper Belt that are larger than 965 kilometres across have companions. These bodies provide insight into how moons formed in the young solar system.

The discovery was made thanks to the combined powers of three space observatories, including NASA’s Hubble Space Telescope. According to astronomers behind the discovery, when these celestial objects were created billions of years ago, collisions must have been more frequent, and that’s a constraint on the formation models.

If there were frequent collisions, then it was quite easy to form these satellites. The objects most likely slammed into each other more often because they inhabited a crowded region.The team uncovered the moon in archival images of 2007 OR10 taken by the Hubble Telescope. Observations taken of the dwarf planet by NASA’s Kepler Space Telescope first tipped off the astronomers of the possibility of a moon circling it.

Kepler revealed that 2007 OR10 has a slow rotation period of 45 hours. Typical rotation periods for Kuiper Belt Objects are under 24 hours.

“We looked in the Hubble archive because the slower rotation period could have been caused by the gravitational tug of a moon. The initial investigator missed the moon in the Hubble images because it is very faint,” one of the authors said.

The astronomers spotted the moon in two separate Hubble observations spaced a year apart. The images show that the moon is gravitationally bound to 2007 OR10 because it moves with the dwarf planet, as seen against a background of stars.

The astronomers calculated the diameters of both objects based on observations in far-infrared light by the Herschel Space Observatory, which measured the thermal emission of the distant worlds.The dwarf planet is about 1,528 kilometres across, and the moon is estimated to be 240 kilometres to 400 kilometres in diameter.

2007 OR10, like Pluto, follows an eccentric orbit, but it is currently three times farther than Pluto is from the sun.2007 OR10 is a member of an exclusive club of nine dwarf planets. Of those bodies, only Pluto and Eris are larger than 2007 OR10.